Comparing bacterial genomes implies the use of a dedicated measure. It relies on comparing circular genomes based on a set of conserved genes. Following this assumption, the common interval appears to be a good candidate. For evidences, we propose herein an approach to compute the common intervals between two circular genomes that takes into account duplications. Its application on a concrete case, comparing E. coli and V. cholerae, is accurate. It indeed emphasizes sets of conserved genes that present high impacts on bacterial functions.